Micro channel devices include, but are not limited to, devices which carry a small volume of a sample for processing and/or analysis. Micro channel devices have been used in biochips, labs-on-a-chip, inkjet printheads, and other micro based technologies. In some instances, a temperature of a sample in a micro channel of a micro channel device is controlled so that it is within a predetermined temperature range for processing, analysis, and/or other purposes. Controlling the temperature includes heating and/or cooling the sample at a predetermined rate so that the temperature of the sample is maintained within a predetermined temperature range or cycled between two or more predetermined temperature ranges.
One technique for heating and/or cooling the fluid involves using a Peltier device, which, generally, is a thermoelectric heat pump that transfers heat from one side of the Peltier device to the other side of the Peltier device. With this technique, the Peltier device is placed in thermal contact with the micro channel device, and an appropriate voltage is applied to the Peltier device to create a temperature gradient for transferring heat between the sides of the Peltier device, either away from or towards the micro channel device. The polarity of the applied voltage determines whether the Peltier device heats up or cools down the micro channel device and thus the sample. A foil heater likewise has been placed in thermal contact with the micro channel device.
Unfortunately, a Peltier device (or the like) generally requires good mechanical/thermal contact between the Peltier device and the micro channel device. Such contact may require accurate and precise mechanical alignment and pressure, which may not be readily achieved. Moreover, heat transfer via the Peltier device may be non-uniform through conduction through the side of the Peltier device in mechanical contact with the micro channel device as well controlled thermal conductance can be difficult to achieve.
Furthermore, using such a device may increase the thermal mass that participates in thermal cycling, which may increase the power required to implement thermal cycling. As a consequence, using a Peltier or similar device may increase the overall size of the micro channel device, power consumption and/or dissipation of the micro channel device, and/or the cost of the micro channel device, as well as provide non-uniform and/or relatively slow temperature control. Moreover, the performance of a Peltier devices may degrade over time, for example, due to mechanical damage to the Peltier sub-elements caused by thermal cycling. This can result in non-uniform temperatures across the surfaces of the Peltier device, which can cause undesirable temperature variations within the micro channel device.